RoundTripTester

Module

"io.kevinlee" %% "extras-hedgehog-circe" % "0.46.1" % Test

or for Scala.js:

"io.kevinlee" %%% "extras-hedgehog-circe" % "0.46.1" % Test

Test JSON Encoder and Decoder

RoundTripTester tests the available Circe JSON Encoder and Decoder by:

• Encoding the given type A into a JSON String using Encoder[A].
• Decoding the JSON String back into the original type A using Decoder[A].

RoundTripTester(sometypeA).test()
// hedgehog.Result

Examples:

import extras.hedgehog.circe.RoundTripTester

import cats._
import io.circe._

import hedgehog._
import hedgehog.runner._

object SomethingSpec extends Properties {
  override def tests: List[Test] = List(
    property("round-trip test Something JSON Codec", roundTripTest),
    property("round-trip test Something JSON Codec - failure case", roundTripTestWithDecodeFailure),
    property("round-trip test Something JSON Codec - failure case (indent 8)", roundTripTestWithDecodeFailureIndent8),
  )
  
  def roundTripTest: Property =
    for {
      something <- genSomething.log("something")
    } yield {
      RoundTripTester(something).test()
    }

  def roundTripTestWithDecodeFailure: Property =
    for {
      something <- genSomething
        .map(something => SomethingWithDecodeFailure(something.id, something.name))
        .log("something")
    } yield {
      RoundTripTester(something).test()
    }

  def roundTripTestWithDecodeFailureIndent8: Property =
    for {
      something <- genSomething
        .map(something => SomethingWithDecodeFailure(something.id, something.name))
        .log("something")
    } yield {
      RoundTripTester(something)
        .indent(8)
        .test()
    }

  def genSomething: Gen[Something] =
    for {
      id <- Gen.int(Range.linear(1, 100))
      name <- Gen.string(Gen.unicode, Range.linear(3, 20))
    } yield Something(id, name)


  final case class Something(id: Int, name: String)
  object Something {
    implicit val somethingShow: Show[Something] =
      something => s"Something(id = ${something.id.toString}, name = ${something.name})"

    implicit val somethingCodec: Codec[Something] = io.circe.generic.semiauto.deriveCodec
  }


  final case class SomethingWithDecodeFailure(id: Int, name: String)

  object SomethingWithDecodeFailure {
    implicit val somethingWithDecodeFailureShow: Show[SomethingWithDecodeFailure] =
      somethingWithDecodeFailure =>
        List(
          s"id = ${somethingWithDecodeFailure.id.toString}",
          s"name = ${somethingWithDecodeFailure.name}",
        ).mkString(
          "SomethingWithDecodeFailure(",
          ", ",
          ")",
        )

    implicit val somethingWithDecodeFailureEncoder: Encoder[SomethingWithDecodeFailure] =
      io.circe.generic.semiauto.deriveEncoder

    implicit val somethingWithDecodeFailureDecoder: Decoder[SomethingWithDecodeFailure] =
      Decoder.instance(c =>
        for {
          id   <- c.downField("blah").as[Int]
          name <- c.downField("name").as[String]
        } yield SomethingWithDecodeFailure(id, name)
      )
  }

}


// This is only for this document so you don't need this.
SomethingSpec.main(Array.empty)
// Using random seed: 100833991189
// + repl.MdocSession$MdocApp0$SomethingSpec$.round-trip test Something JSON Codec: OK, passed 100 tests
// - repl.MdocSession$MdocApp0$SomethingSpec$.round-trip test Something JSON Codec - failure case: Falsified after 0 passed tests
// > something: SomethingWithDecodeFailure(1,���)
// > Round-trip test for SomethingSpec.SomethingWithDecodeFailure failed with error:
// > Error: DecodingFailure at .blah: Missing required field
// > ---
// > Input: SomethingWithDecodeFailure(id = 1, name = ���)
// > ---
// > JSON: {
//   "id" : 1,
//   "name" : "\u0000\u0000\u0000"
// }
// >
// - repl.MdocSession$MdocApp0$SomethingSpec$.round-trip test Something JSON Codec - failure case (indent 8): Falsified after 0 passed tests
// > something: SomethingWithDecodeFailure(1,���)
// > Round-trip test for SomethingSpec.SomethingWithDecodeFailure failed with error:
// > Error: DecodingFailure at .blah: Missing required field
// > ---
// > Input: SomethingWithDecodeFailure(id = 1, name = ���)
// > ---
// > JSON: {
//         "id" : 1,
//         "name" : "\u0000\u0000\u0000"
// }
// >